Flame barrier device

ABSTRACT

A flame-barrier device has a plurality of openings that are essentially parallel relative to a flow of substance passing therethrough, the device being made up of an assembly of a plurality of pierced disks whose openings co-operate with adjacent corresponding openings to form through channels.

The present invention relates to a flame-barrier device that is intendedto prevent flames propagating or to prevent an explosion frontpropagating at a determined location.

1. Field of the Invention

More precisely, the invention relates more particularly to such a devicesuitable for being installed in pipes that serve to convey a gaseoussubstance or a mixture of such substances that are flammable orexplosive.

2. Background of the Invention

In systems for recovering hydrocarbon vapor, e.g., those relating todispensing gasoline, there is a requirement that flame barriers shall beinserted in ducts that convey an explosive mixture of air and gaseoushydrocarbons in order to prevent propagation of flames or of anexplosion front. Flames, and worse, an explosion can be created in sucha gasoline pump by other apparatuses requiring mechanical or electricalpower for their operation. This applies in particular to the pumpsproper where parts in relative motion can give off sparks by shock.Similarly, a source of heat can give rise to deflagration of saidexplosive gaseous mixture which it is important to confine in space andprevent from propagating.

In such flame barriers, it is desired to produce a flame-throttlingeffect by causing the incandescent gases to pass through a plurality ofsmall-diameter ducts that are long relative to their diameter and thatare made of materials having high thermal conductivity, high specificheat, and a large heat exchange area. That leads immediately to a dropin the temperature of the gas and stops propagation. In all cases it isdesirable to make holes that are long and small in diameter, which isvery difficult to do using conventional techniques.

Such flame barriers are already known constituting some quantity ofsmall-diameter metal tubes stacked together in a bundle and heldtogether by welding or by adhesive. The set of individual tubes may befixed inside a ring, with the assembled flame barrier being essentiallyround and symmetrical in shape, e.g., having the shape of a disk.Nevertheless such devices are expensive.

U.S. Pat. No. 4,484,690 discloses a flame-barrier device constituted byan assembly of several disks pierced by holes and spaced apart byspacers, with the openings through the disks being disposed in astaggered configuration.

United Kingdom patent No. 723 936 describes a flame-barrier deviceprovided with a plurality of openings that are essentially parallelrelative to a flow of substance passing therethrough, the device beingconstituted by an assembly comprising a plurality of pierced disks whoseopenings are in alignment. In that known device, the pierced disks areseparated by disks or sheets of fine gauze.

Another known type of such a flame barrier consists in winding apreviously corrugated tape onto a cylindrical central part. The turns ofthe winding are kept apart by winding them simultaneously with a flattape. The spiral-wound corrugated tape whose turns are held apart by theflat tape forms a disk which is fixed inside a ring. The corrugationsmay be parallel to the central axis of the flame barrier, therebyproviding passages parallel to the flow direction of the substancepassing therethrough, or they may be at an inclination relative to thecentral axis.

As described, that method of obtaining such a flame barrier remainsquite expensive and suffers from the severe drawback of giving rise to adevice that can itself be deformed by the pressure wave of adeflagration or an explosion, tending to extrude the individual turnsrelative to one another by sliding.

SUMMARY OF THE INVENTION

The object of the present invention is thus to provide a flame-barrierdevice which is guaranteed to operate also under explosion conditionsbecause of its stability and resistance to deformation, and which isnevertheless easy to manufacture and therefore cheaper.

To achieve this object, the invention provides a flame-barrier deviceprovided with a plurality of openings that are essentially parallelrelative to a flow of a substance passing through the device, the devicebeing constituted by an assembly of a plurality of pierced disks whoseopenings are in alignment, and being remarkable in that pierced disksare stacked to form a bundle, and in that the openings of the disks comeinto alignment in such a manner as to co-operate with adjacentcorresponding openings to form parallel through channels.

The advantage of a flame barrier of the invention is that it can beadapted easily to varying operating conditions relating to itsdurability, its specific heat, and its heat exchange surface area. Inaddition, the invention makes it possible to combine disks of differentmaterials in order to adapt the flame barrier of the invention to theexpected operating conditions. For this purpose, such a flame barrier isconstituted by at least one metal disk and/or at least one ceramic disk,for example.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear from thedependent claims and also from the following description of variousembodiments of the invention given as nonlimiting examples. Thedescription refers to the accompanying figures, in which:

FIG. 1 is a plan view of a first embodiment of the flame-barrier deviceof the invention;

FIG. 2 is a side view of the FIG. 1 device;

FIG. 3 is a side view of a second embodiment of the invention;

FIG. 4 is a section view on a larger scale showing a feature of the FIG.3 device on the section line marked IV-IV in FIG. 3;

FIG. 5 is a side view of a third embodiment of the invention; and

FIG. 6 is a section view of yet another embodiment which has the sameside view as that of the FIG. 2 embodiment. For convenience, the sectionview for FIG. 6 is illustrated as being taken on the section line markedVI--VI in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a flame-barrier device 10 of which there can be seen apreferably metal disk 12 provided with a plurality of holes 14. Theholes 14 are made by drilling, stamping, forging, punching, or molding.The holes 14 are preferably of identical diameter that is comparativelysmall relative to the diameter of the disk 12. The set of said holes 14is to prevent flames or an explosion front from propagating; however itmust also allow the flowing substance to pass through without impedingpassage thereof. When the device is a flame barrier 10 for use in asystem for recovering hydrocarbon vapor having disks 12 of a radius R ofabout .mm, it is preferable to make several hundreds of holes 14 eachhaving a diameter of about 0.6 mm to 0.7 mm.

As shown in FIG. 2, the flame-barrier device 10 is made up of aplurality of pierced disks 12 which are stacked together to form abundle. In order to facilitate mounting the disks 12 so that the holes14 come into alignment, thereby forming channels that are essentiallyparallel relative to the centerline LC, several reference marks arepreferably placed on the disks 12. The easiest reference marks to makeare holes of some reasonable diameter greater than that of the otherholes 14 and likewise parallel to the centerline LC. By way of example,FIG. 1 shows two such reference marks that also serve to receive tworivets 16 (as can also be seen in FIG. 2) for fixing the disks 12together.

Another method of the invention consists in fixing disks 112 whileattaching them to one another by means of studs 18 as shown in FIGS. 3and 4. In particular, FIG. 4 shows how embossed studs 18 serve asreference marks for determining the position of one disk 112a relativeto another disk 112b or 112b relative to 112c, for example, and also forthe purpose of interfitting and making up the bundle that constitutesthe flame-barrier device 110.

FIG. 5 shows a third way of fixing a plurality of disks 212 in a ring 20so that the disks are stacked to constitute the flame-barrier device 210of the invention. In this case there is a circle made of metal, forexample, surrounding the periphery of the disk 212 with the edgeportions 22 of the circle being placed so that they extend towards thecenterline, encompassing and securing the disks 212. Although notvisible in FIG. 5, the disks 212 clearly need to have reference marks asexplained above.

All of the embodiments of the invention described so far are associatedwith flame-barrier devices each in the form of a fixed disk: its outerperiphery is uniform, smooth, and even. Such flame barriers aretypically used inside pipes where they are placed in shaped locations.However, it is also possible for a flame-barrier device of the inventionto have a ring which serves not only for fixing the individual diskstogether but also includes remote edge portions 22 that act as sleeves,e.g., for interconnecting lengths of pipe. Under such circumstances, theflame barrier should be provided with at least one disk that is ofgreater diameter than the others.

In addition, another possibility for integrating the flame-barrierdevice 110 of the invention in a pipe system is shown in FIG. 3. In thisexample, two disks 112X located substantially in the middle of the flamebarrier 110 have an outside diameter that is greater than that of thediameters of the other disks 112. The peripheral sections of the disks112 adjacent to the disks 112X can thus serve as seats for two pipes 24and 26. The flame barrier 110 also serves to interconnect the two pipes24 and 26 without impeding its main function.

Finally, FIG. 6 shows another embodiment of the invention. In order tomake FIG. 6 easier to draw and to concentrate on essential details only,FIG. 6 shows only five disks 412a, 412b, 412c, 412d, and 412e plus twoseries of adjacent holes 14.1a-e and 14.2a-e as examples of the assemblyconstituted by the flame barrier 10. In this case, the disks 412a-e areslightly offset relative to one another as are the holes 14.1a-e and14.2a-e.

Consequently, the channel formed by the series of holes 14.1a-e isinclined slightly relative to line LCa which represents the centerlineof the flame barrier 410, as indicated by angle α. For the main purposeof the flame barrier 410, the configuration of FIG. 6 gives theadvantage that the speed of a flame front or of an explosion reachingthe flame barrier is prevented from propagating along the samedirection. The inclination relative to the flame propagation directionweakens the energy of the front in combination with the obstaclescreated by said steps formed by the edges of the holes 14.1a-e and14.2a-e projecting into the channels.

Also, the increase in the internal surface area of each channel ascreated by offsetting the disks in this way assists the effect wherebyflame (or explosion) energy is reduced by heat exchange.

To increase the specific heat of the flame barrier 410 of the invention,and as shown by way of example in FIG. 6, it is possible to includebetween the disks 412c and 412e a disk 412d of a nonmetallic material,preferably a ceramic. Without limiting the concept of the invention inany way, it is clear that it is possible to use a plurality of suchdisks that are ceramic or more generally nonmetallic.

From all of the embodiments of the present invention described above andthat are roughly cylindrical in shape, it is easy to imagine buildingflame barriers of other shapes: e.g., rectangular, in order to fit thembetter to types of channel other than round channels.

In all cases, the advantage of a flame-barrier device of the inventionconsists firstly in its low cost price and secondly in its strength. Nodeformation of the flame barrier is to be feared in the event of apressure wave coming from an explosion acting on one of the faces of thedevice.

We claim:
 1. A flame-barrier device (10) comprising: a plurality ofopenings (14) that are essentially parallel relative to a flow of asubstance passing through the device, and an assembly of a plurality ofpierced disks (12) include said openings (14) in alignment, said pierceddisks (12) being stacked to form a bundle, wherein the openings (14) ofthe disks (12) come into alignment in such a manner as to co-operatewith adjacent corresponding said openings (14) to form parallel throughchannels.
 2. A flame-barrier device according to claim 1, wherein eachsaid disk (12) includes the same number of said openings (14) organizedin the same configuration.
 3. A flame-barrier device according to claim2, wherein the openings (14) are holes of the same diameter.
 4. Aflame-barrier device according to claim 2, wherein the openings (14)through the disks (12) are manufactured by drilling, stamping, forging,punching, or molding.
 5. A flame-barrier device according to claim 2,wherein said opening (14) through a said disk (12) is accurately inalignment with an adjacent and corresponding opening of an adjacent saiddisk.
 6. A flame-barrier device according to claim 2, wherein each saidopening (14.1a-e) of a said disk (4.1a-e) is slightly offset relative toan adjacent and corresponding opening of an adjacent said disk.
 7. Aflame-barrier device according to claim 1, wherein at least one of thedisks (12) is made of a metal.
 8. A flame-barrier device according toclaim 1, wherein at least one of the disks is made of a ceramic.
 9. Aflame-barrier device according to claim 1, wherein at least one of thedisks (112X) is of a diameter greater than that of other said disks. 10.A flame-barrier device according to claim 1, wherein the disks (112)forming said device (110) are stacked on one another in a releasablemanner.
 11. A flame-barrier device according to claim 1, wherein thedisks (12) forming said device (10) are fixed to one another by at leastone of rivets (16) and studs (18).
 12. A flame barrier device accordingto claim 1, wherein the disks (212) forming said device (210) are fixedtogether by a ring (20) which surrounds the assembly of the disks at aperiphery of said disks.